A three-phase permanent magnet-type synchronous motor typically employs a motor where 2N/3P is an integer assuming that the number of magnetic poles in a rotator is P and the number of slots in a stator is N. However, this type of motor has a problem with a large cogging torque. Therefore, to reduce this cogging torque, a technique is proposed. This technique employs a fractional-slot motor where 2N/3P is not an integer and specifies the combination of the number of magnetic poles P and the number of slots N so as to reduce the cogging torque.
For example, Patent Literature 1 discloses that N/P is set to satisfy 1<N/P≤1.2 assuming that the number of magnetic poles is P and the number of slots is N so as to reduce the cogging torque.
Patent Literature 2 discloses that the number of slots N is set to satisfy N=3×[P/2−INT (P/10)] assuming that the number of magnetic poles is P and the number of slots is N so as to reduce the cogging torque. However, INT (P/10) denotes a value of the quotient of P divided by 10.